The present invention relates generally to wireless networks, and more particularly to self-healing in a wireless mobile ad-hoc network.
Most commercial public wireless networks contain a significant amount of network infrastructure which allows mobile wireless devices (e.g., wireless telephones) to communicate with each other as well as with other networks (e.g., a wired telephone network). In such networks, the infrastructure, which includes components such as base stations and other network controllers, handles network control and routing operations. The locations of the network infrastructure components are fixed, and the locations of the various components are designed to provide a desired level of network performance. Thus, each wireless device communicates directly with fixed network infrastructure components or uses the fixed infrastructure to connect it to other devices for subsequent communication.
In areas where there is little or no communication infrastructure, wireless devices may communicate with each other by organizing into an ad-hoc wireless network. Mobile ad-hoc wireless networks have no central control or system administrative support (for network setup, configuration and operations), and each wireless device which is part of the network operates as an individual communication device as well as part of the network infrastructure. Thus, each wireless device may originate and receive messages, but each wireless device also functions to route messages between other wireless devices which may otherwise be unable to directly communicate with each other. Instead of relying on wireless network infrastructure for communication, mobile ad-hoc wireless networks rely on peer-to-peer interactions for network communication. There are many applications for mobile ad-hoc wireless networks. For example, military personnel on the field of battle; emergency disaster relief personnel coordinating efforts where there is no wireless infrastructure; informal gatherings where participants wish to communicate with each other; and sensor networks where sensor elements scatter randomly to form an ad-hoc network for on-demand communication purposes. It is also noted that mobile ad-hoc wireless networks are useful for devices other than telephones, for example wireless PDAs, computers, sensors, or any other type of communication device.
The varying network topology of a mobile wireless ad-hoc network complicates various network functions, for example data packet routing. In a conventional wireless network, which utilizes fixed network infrastructure, the topology of the network is static, and each of the routing nodes in the network maintains network topology information to assist in the routing determination. However, the network topology in a mobile wireless ad-hoc network changes dynamically, with new links being created and existing links being torn down, as each of the wireless devices moves around in the network. Thus, nodes in a mobile ad-hoc network function in an inherently unreliable environment, with unpredictable changes causing node and route failures. As a result, nodes need to autonomously adjust their operating parameters in order to ensure that critical information is reliably delivered despite the unreliability of the network. This autonomous adjustment of a network node in order to dynamically adjust and compensate for degradations in network services is referred to as “self-healing” of network nodes. More specifically, self-healing is the ability of the network to autonomously detect non-malicious network-related problems encountered while transporting applications and data through the network, and to take corrective actions in response to such problems, without participation of human administrators or users. Examples of non-malicious network-related problems include hard failures (i.e., failure/malfunctioning of one or more network elements) and soft failures (i.e., loss in network connectivity due to performance degradation caused by the dynamics/unpredictability of the underlying communications network). Such self-healing ability is enabled by a set of operations, to be performed by network nodes, which are designed to detect and correct specific network-related problems.
There have been prior attempts at self-healing in mobile ad-hoc wireless networks. For example, prior self-healing routing protocols have been designed to establish new routes to maintain system connectivity as node failures and mobility change the topology of the network. However, one of the problems with prior self-healing protocols is that they originated from wired network protocols. Assumptions that are valid in wired networks, such as the notion that all destinations are unique and that the best route at the start of the transmission will be the best route through the duration of the transmission, are no longer valid for mobile ad-hoc wireless networks. Thus, these prior attempts are unable to effectively deal with situations in which a data packet destination becomes unreachable after the data packet is initially transmitted.
Self-healing has also been applied at the hardware level, generally through the use of redundant back-up systems which activate upon a hardware failure. However, self-healing at the hardware level is generally expensive in terms of equipment, area, financial cost, and energy. Further, due to the transient nature of mobile ad-hoc wireless networks, redundant hardware self-healing is not always a practical approach.
There is a need for improved self-healing techniques in mobile ad-hoc wireless networks.